Past studies have shown that oral or nasal application of tolerogens can induce peripheral tolerance, and these methods have been successfully used for treatment of allergies. One limitation of such approaches is relatively large amounts of materials are often needed to successfully tolerize the host. To enable a more efficient method to deliver tolerogens, we have devised a single dose method to induce oral or nasal tolerance to stimulate the induction of regulatory T cells. Previous studies have shown that M cells on mucosal inductive tissues are required for oral tolerance, and in the absence of Peyer[unreadable]s patches, tolerance cannot be induced. Thus, we hypothesized that targeting mucosal inductive tissues is important for tolerance induction. Using an M cell ligand to test this hypothesis, proteins genetically fused to the adhesin or hemagglutinin protein from reovirus serotype 3, protein s1 (ps1), tolerize the host. Our data show that oral or nasal application of the fusion protein, ovalbumin (OVA)- ps1, stimulates T and B cell unresponsiveness to OVA. Given these findings, we hypothesize that ps1 delivered autoantigens can induce tolerance to treat autoimmune diseases. To enable this effort, studies in Specific Aim 1 are focused on learning the mechanisms for T cell unresponsiveness following mucosal application of myelin oligodendrocyte glycoprotein fused to ps1 (MOG-ps1) and testing its ability to prevent or treat experimental autoimmune encephalomyelitis (EAE). Studies in Specific Aim 2 will determine the responsible regulatory T cell subset(s), which when adoptively transferred, can confer protection against EAE challenge. Studies in Specific Aim 3 will determine the responsible dendritic cell subset that supports regulatory T cell development.